Thermal sensitive element



J- 5. WINTER THERMAL SENSITIVE ELEMENT Sheet f .7512

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chi 225.25. i4 2zzz /WL\TTORNEYS Jan. 7, 1969 Filed June 8. 1966 Jan. 7, 1969 J. 5. WINTER THERMAL SENSITIVE ELEMENT Filed June 8,

PRIOR ART Jazzazs'fl @2236! QYJQZZ 42 t g a vr'romwiys United States Patent 3,420,105 THERMAL SENSITIVE ELEMENT James S. Winter, Springfield, Ohio, assignor to Vernay Laboratories, Inc., Yellow Springs, Ohio, a corporation of Ohio Filed June 8, 1966, Ser. No. 556,161

US. Cl. 73368.3 Int. Cl. G01k 5/32; Ftllb 19/00; F16j 3/00 This invention relates to a thermal power unit and in particular relates to a thermal power unit of the squeezepush type wherein the well for holding the power piston has a novel shape for resisting bending of the squeeze boot after extension of the power piston.

Squeeze-push type thermal power units generally employ a casing for holding a thermally expansible wax or the like and a resilient boot for being operably mounted in the casing to coact with the thermally expansible wax for squeezing a power piston out from a well formed within the boot. The boot may have a peripheral bead for mounting the boot within the casing and a base portion extending beneath the bead for being immersed in the thermally expansible wax. The base portion is held in spaced relation with the sides of the casing, and the thermally expansible wax acts at the outside of the base portion for compressing the boot to extend the piston upon a temperature rise ambient the casing.

To assure that the pressure exerted by the thermally expansible wax is directed for squeezing the piston out from the associated well, the base of the well is generally formed to have a spade-shaped configuration for converting the squeezing action into a continuous upward pressure on the piston. However, the well may also be formed with a conical or hemispherical shaped base.

It has been found that the use of the spade-shaped or conical configuration at the base of the well causes the boot to collapse about a single plane which tends to weaken the lateral strength of the boot. The result is that with the boot collapsed along a single plane, slight variations in pressure developed by the thermally expansible wax causes the boot to bend within the casing such that the axis of the well is substantially misaligned after the extension of the piston.

With the axis of the well misaligned within the casing after extension of the power member, retraction of the power member becomes more diflicult and less predictable than would be possible if the axis of the well were maintained in a substantially aligned condition.

Also, the twisting or bending of the base portion of the resilient boot causes a bulb to be formed at the lower portion of the boot which is pushed ahead of the retracting power member and which, therefore, causes stretching of the upper portions of the boot to accommodate the retraction of the power piston. Since the upper portion of the boot is generally used to seal the interior of the casing from outside dust, water and the like, the stretching of the upper portion of the boot tends to disturb the seal and permit the entry of foreign matter into the casing which further aggravates the operation of the thermal power unit.

In addition to the unpredictability of operation and to the disturbance or destruction of the sealing effect of the boot, the bending or misalignment of the base portion of the boot causes the retraction of the power member to produce unnecessary wear at the inner surface of the well. This is because the bent portion of the boot tends to remain misaligned, and the retraction of the power member is directed into the side wall of the boot rather than into the well. In fact, extreme bending of the lower portion of the boot can cause the side wall to be punctured, hence, destroying the operation of the thermal power unit.

In addition to the several disadvantages associated with 19 Claims ice the misalignment of the base portion of the boot after the extension of the power member, the folding of the boot about a single plane, as induced by the spade-shaped configuration of the base of the well, generates undesirable stresses at the outside corners of the fold. Essentially, the pressure applied to the boot due to a rise in temperature ambient the thermally expansible material causes the normally cylindrical boot to be substantially flattened with the result that cracks and breaks may occur at highstress regions developed at the folded edges.

Accordingly, it is a principal object of this invention to provide a resilient boot for a squeeze-type thermal power unit which has a novel boot structure for decreasing the operation stresses of the power unit.

It is also an object of this invention to provide a resilient boot for a squeeze-push thermal power unit wherein the boot is provided with a well having flat sides and fold angles for causing the boot to collapse in a predetermined stress pattern.

It is another object of this invention to provide a resilient boot for a squeeze-push type thermal power unit wherein the well for holding the thermal power piston has a triangular cross-sectional profile for causing the boot to collapse along three distinct planes to improve the predictability of the operation of the power unit and to increase the longevity of the resilient boot.

It is a further object of this invention to provide a resilient boot for a squeeze-push type thermal power unit wherein the boot has a polygonal well, the sides of which converge to form a common vertex at the base of the well for causing the boot to collapse in such a manner as to develop longitudinal ribs on the exterior surface of the boot for resisting bending or twisting thereof in response to pressures applied by a thermally actuating substance.

It is an additional object of this invention to provide a resilient boot for a thermal power unit having a well with a polygonal cross-section and having a power piston for being received internally of the well which piston has a cylindrical diameter greater than the diameter of the largest circle circumscribed by the polygonal cross-section of the well.

It is also an object of this invention to provide a thermal power unit employing a resilient boot having a well formed therein for receiving a power piston wherein the well has a polygonal cross-section at the base portion of the boot and a cylindrical cross-section at the upper portion of the boot and wherein the power piston has a cylindrical configuration for being fitted snugly within the entire length of the well.

These and other objects, features and advantages of the present invention will be understood in greater detail from the following description and the associated drawings wherein reference numerals are utilized in designating an illustrative embodiment and wherein:

FIGURE 1 is a sectional view of a thermal power unit showing the workable relationship of a resilient boot and an associated power piston according to this invention;

FIGURE 2 is an exploded view of the thermal power unit of FIGURE 1;

FIGURE 3 is a sectional view of a resilient boot and an associated power member of a prior art structure wherein the power member or piston has been extended from the boot and wherein the pressure applied at the outside of the base portion of the boot has caused misalignment or bending of the boot;

FIGURE 4 is a sectional view of the prior art form as taken along the line IVIV of FIGURE 3;

FIGURE 5 is a cross-sectional view similar to the view of FIGURE 4 with the power piston removed from the boot and with the boot maintained in an unstressed condition;

FIGURE 6 is a sectional view of the base portion of the prior art form shown in FIGURE 3 after the power piston has been substantially extended from the boot and under conditions of maximum compression of the thermally expansible substance associated with the thermal power unit; this view is taken along the line VIVI of FIG- URE 3;

FIGURE 7 is a sectional view of a resilient boot according to this invention as would appear in a thermal power unit after expansion of the associated thermally expansible substance and after compression of a portion of the boot for extending the power piston therefrom;

FIGURE 8 is a sectional view of the resilient boot and power member structure as taken along the lines VIII- VIII of FIGURE 7;

FIGURE 9 is a sectional view of the resilient boot-of FIGURE 7 when the boot is in an unstressed condition and when the power member is removed from the associated well. Under such circumstances, the sectional view of FIGURE 9 would be taken along lines similar to the sectional view of FIGURE 8; and

FIGURE 10 is a sectional view of the resilient boot of this invention as taken along the lines X-X of FIG- URE 7 showing the collapsed nature of the base portion of the resilient boot in response to forces applied at the outside of the boot by the thermally expansible substance of FIGURE 1.

This invention concerns generally a resilient boot for being employed in a squeeze-push thermal power unit wherein the boot is provided with means for causing the folding or collapsing of the boot to take place in a predetermined pattern for reducing the operation stresses of the thermal power unit. By providing the well of the resilient boot, for instance, with a triangular configuration as viewed in cross section, the boot can be caused to collapse along three planes rather than a single plane, with longitudinal ribs or protuberances formed along the outside of the boot for resisting bending or misalignment of the boot in response to pressures exerted thereon by an associated thermally expansible substance.

A thermal power unit has a resilient boot 21 embodying the features and advantages of the present invention.

The thermal power unit 20 has a lower casing 22 and an upper casing 23 which are securely mounted together at flanges 24 and 25, respectively. The flange 24 has an upwardly extending rim 26 which may be folded about the flange as at 27 for securing the upper and lower casings together.

The resilient boot 21 has an annular head 22 which is sandwiched between the flanges 24 and 25 of the casings 22 and 23, and, accordingly, the boot 21 is rigidly positioned within the cavity formed by the respective casings.

The boot 21 has a well 29 for receiving a power piston 30. The power piston 30 extends into the well 29 through a guide opening 31 formed centrally of the upper casing 23. The piston 30 is preferably of a larger diameter than the well 29, however, the piston may have a smaller diameter without interferring with the novel folding action of the boot 21. The interior of the lower casing 22 is filled with a thermally expansible substance 32 such as a thermally expansible wax or the like which, upon rises in temperature, will exert a pressure at the outside surface of the boot for squeezing the piston outwardly from the well 29 and pushing the boot and piston ahead of the expanding wax.

The detailed structure of the components forming the thermal power unit of FIGURE 1 may be seen more clearly in the exploded view of FIGURE 2. In particular, the flange 24 of the lower casing 22 has a grip surface 33 consisting of a pair of V-shaped concentric grooves 34. Similarly, the flange 25 of the upper casing 23 has a grip surface 35 consisting of a pair of concentric V-shaped grooves 36. When the bead 22 of the resilient 4 boot 21 is sandwiched between the flanges 24 and 25 of the lower and upper casings as shown in FIGURE 1, the resilient material extrudes within the V-shaped grooves 34 and 36 for forming a pressure seal between the respective casings as well as for rigidly positioning the resilient boot 21 within the interior of the casings.

The resilient boot 22 has a base portion 37 depending from the lower surface of the bead 22 and tapering to a rounded end 38. As shown in FIGURE 1, the tapered sides of the base portion 37 maintain the boot in spaced relationship with the inner surface 39 of the lower casing 22. Also, the rounded end 38 of the boot 21 is maintained in spaced relationship with the lower surface 40 of the casing 22. In this way, the thermally expansible substance 32 is disposed about the entire base 37 of the boot for exerting transverse pressures thereon to squeeze the piston 30 from the well 29.

The resilient boot 21 has a truncated conical upper portion 41 and an integral cylindrical neck portion 42. Similarly, the inside of the upper casing 23 has a truncated conical surface 43 and a cylindrical surface 44 for conforming with the surfaces 41 and 42 of the boot 21. In addition, the cylindrical surface 44 of the interior of the casing 23 has a pair of V-shaped grooves 45 formed similarly to the V-shaped grooves 34 and 36 for causing the neck portion 42 of the boot 21 to extrude therein in order to form a pressure seal between the casing 23, the boot 21, and the power piston 30. In this way, the guide opening 31 associated with the piston 30 can be closed from external dust, fluids and the like.

The neck portion 42 of the boot 21 terminates in a flat end wall 46, and an anti-chafe ring 47 is disposed between the end wall 46 and a similar end wall 48 associated with the interior of the upper casing 23.

The power piston 30 is cylindrical in configuration and has a conical end portion 49 which is received within the Well 29 of the boot 21. Unlike the configuration of the power piston 30, the configuration of the inner surface of the well 29 is irregular and has been shaped to produce a predetermined folding action for the base portion 37 of the boot in response to rises in temperature ambient the thermally expansible material 32.

The well 29 has a cylindrical cross-sectional profile from the end face 46 of the boot 21 to a point 50. From the point 50 to the base of the well, the cross-sectional profile is triangular as is evident by the plane side walls 51. The walls 51 converge at a common vertex as at 52 such that a cavity is formed at the base of the well having an inverted pyramidal configuration. The effect of the triangular cross-sectional profile of the well 29 can be understood from a comparison of the prior art FIGURES 3 through 6 with the corresponding FIGURES 7 through 10 showing a resilient boot according to this invention.

In FIGURE 3, a resilient boot 53 has a well 54 for holding a realtively extensible power piston 55. When the boot is in a non-stressed condition, such as when the boot is removed from the thermal power unit, the well 54 is substantially cylindrical in form as shown in FIGURE 5. When the power member 55 is inserted within the Well 54, the resilient boot 53 retains its cylindrical configuration both at the external surface 56 and at the inner surface defining the well 54.

However, when the prior art boot 53 is disposed in an operational thermal power unit, extension of the power member 5'5 will cause the well 54 to fold or collapse along a single plane as at 57. The particular plane about which the boot folds is determined by the spade-shape or chiselshape of the lower end of the well. In the prior art structure, the spade-shape at the lower end of the well was provided to enable the transverse pressures of the thermally expansible substance within the power unit casing to exert a pressure on the boot which would gradually urge the piston 55 outwardly from the well 54.

The folding of the prior art boot about the plane 57, as shown in FIGURE 6, has not been entirely satisfactory in that such a folding may produce high stress regions as at 58 and 59. After repeated use the areas 58 and 59 may tend to crack or split thereby defeating the proper operation of the power unit. Also, the fact that the resilient boot folds along the plane 57 weakens the resistance of the boot to pressure supplied transversely of the base portion 60. The result is that the base portion 60 may be bent or misaligned from the remainder of the boot after the piston 55 has withdrawn as shown in FIGURE 3.

When the power unit cools permitting a return spring or the like to cause the power member 55 to retract within the well 54, the bent or misaligned portion 60 of the boot 53 may resist the retraction motion of the piston. As the piston forces its way into the misaligned well 57, a bulb 61 forms at the lower end of the boot, and the entire misaligned section tends to be pushed ahead of the retracting piston. The result is that the upper portion of the boot, as at 62, begins to stretch downwardly within the associated casing, and the neck portion 63, accordingly, breaks its seal with the casing and with the power member 55.

Once the seal at the neck portion 63 is broken, dust, water and the like can enter the power unit for further aggravating the operation thereof. In addition, the retraction of the power member 55 with the lower portion of the boot 60 misaligned, as in FIGURE 3, causes the power member to develop excessive wear at the inner surface of the well 54 in the region of the misaligned portion 60. If, in fact, the base portion 60 is sufficiently misaligned, the power member 55 in retracting into the well 54 could puncture the wall of the boot and destroy the operation of the power unit. In conditions of less serious misalignment, the retraction of the power member 55 tends to make the operation of the power unit less predictable and less reliable.

In contrast with the resilient boot 53 of the prior art structure as shown in FIGURES 3 through 6, the resilient boot 21 of FIGURES l and 2 as illustrated in FIGURES 7 through maintains substantial alignment after extension of the power member 30 from the well 29.

The cross-sectional profile of the base portion of the well 29 is triangular in shape, as shown in FIGURE 9, and has plane walls 51 and fold angles 64. As shown in FIGURE 2, the plane walls 51 converge along the fold angles 64 to a common vertex 52. When the power member 30 is fitted within the well 29, the cross-sectional profile of the base portion 37 of the boot 21 takes the form shown in FIGURE 8, and in particular, the cross-sectional profile is substantially cylindrical at the inner surface of the well 29 as at 65 and is substantially triangular in shape at the outer surface as shown at 66. The outer surface of the base portion 37 of the boot 21, as shown in FIGURE 8, may be said to have longitudinal ribs 67 formed due to the stressing of the boot material by the presence of the cylindrical power piston 30.

When the power piston 30 is extended from the well 29 due to a rise in temperature ambient the casing 22, the base portion 37 of the boot 21 folds or collapses along three planes as at 68, 69 and 79 of FIGURE 10. As will be observed, the folded boot of FIGURE 10 does not have the regions of high stress as at 58 and 59 of FIGURE 6. Essentially, the fold is more uniform around the periphcry of the base portion 37.

The result of the triangular fold as shown in FIGURE 10 is that longitudinal ribs or protuberances 71, 72 and 73 are formed along the length of the base portion 37 for resisting bending of the boot or misalignment of the well as was described in connection with FIGURE 3. In FIG- URE 10, it will be noted that one of the protuberances 71, 72 or 73 is formed on one side of all planes which contain the axis of the boot 21. Therefore, regardless of the orientation of bending action attempted to be impressed upon the base portion 37 of the boot 21, at least one of the curved protuberances 71 through 73 will be orientated for resisting that bending action.

Accordingly, when the power member 30 is extended from the well 29 as shown in FIGURE 7, the lower portion of the boot collapses due to the pressure of the thermally expansible substance Within the casing 22, however, the collapse is preorientated in such a manner as indicated by the cross-section of FIGURE 10 to cause the well 29 to maintain substantial alignment under all available pressures experienced by the thermally expansible substance. Accordingly, not only are high stress regions avoided during the folding of the base portion 37 of the boot, but the boot is maintained in a position for receiving the retracting power member 30 in such a manner as to avoid undue stretching of the neck portion 42 and as to avoid undue wear of the inner surface of the well 29 and as to avoid unpredictable operation of the power unit due to increasing the force required to retract the power member 30.

It will be understood that various modifications and combinations of the features of this invention may be accomplished by those versed in the art, but I desire to claim all such modifications and combinations as properly come within the scope and spirit of my invention.

1 claim as my invention:

1. A thermal power unit comprising:

a casing containing a thermally expansible material,

a resilient boot fitted within the casing in operable contact with the thermally expansible material,

a Well formed within the boot for receiving a relatively extensible power piston therein,

said well having an inner cross-sectional profile substantially triangular in configuration, and

a power piston operably disposed within said well and being extended relative to said casing in response to an increase in temperature ambient said thermally expansible material.

2. A thermal power unit in accordance with claim 1 wherein the inner side walls forming said substantially triangular cross-sectional profile of said well converge at a common vertex at the base of the well and wherein said thermally expansible material is confined about said boot to compress said boot in response to a temperature rise ambient said casing, and wherein said boot c01- lapses initially at said common vertex for squeezing the piston from the well.

3. A thermal power unit in accordance with claim 1 wherein said resilient boot has a base portion depending within the casing and spaced from the inner side walls thereof and wherein a portion of said thermally expansible material is maintained about the boot between the depending base portion and the inner side Walls of the casing, said well being formed substantially axially within said boot and extending into said base portion, and said thermally expansible substance exerting lateral forces on said base portion for squeezing said piston from said well in response to a rise in temperature ambient said casing.

4. A thermal power unit in accordance with claim 1 wherein said resilient boot has an external bead and a base portion depending from the head, said head being mounted within said casing in a manner for providing a sealed cavity between said base portion and said casing, said :boot having an opened end formed oppositely of said base portion, said well extending from said opened end into said base portion, and said thermally expansible material filling said cavity for squeezing said piston from said well in response to a rise in temperature ambient said casing.

5. A thermal power unit in accordance with claim 1 wherein said resilient boot has a neck portion and a base portion, said Well extending from said neck portion to said base portion, said power piston having a substantially circular cross-sectional profile, said substantially triangular cross-sectional profile of said well being formed within said base portion and said well having a 7 substantially circular cross-sectional profile formed within said neck portion.

6. A thermal power unit in accordance with claim wherein the inner Walls of said boot forming said well converge at the base of the well into an inverted substantially pyramidal cavity.

7. A thermal power unit in accordance with claim 5 wherein said well terminates within said base portion of the boot at triangular end surfaces meeting at a common vertex.

8. A thermal power unit in accordance with claim 5 wherein the inner side walls forming said substantially triangular cross-sectional profile of said well converge at a common vertex at the base of said well.

9. A thermal power unit comprising:

a casing containing a thermally expansible material,

a resilient boot fitted within the casing in operable contact with the thermally expansible material,

said boot secured to the casin in a manner for forming a sealed cavity between the boot and the casing,

the thermally expansible material disposed within said cavity in a manner for compressing said boot in response to a temperature rise ambient the casing,

a well formed within the boot for receiving a power piston therein,

a number of strain orientating walls formed longitudinally along the inner surface of the well and causing said well to collapse in a predetermined pattern in response to pressure applied against said boot by said thermally expansible material,

each adjacent pair of said strain orientating Walls formiug substantially equal angles, and each of said strain orientating walls being of substantially equal length,

said boot forming a convex longitudinal protuberance on one side of all planes passing through the longitudinal axis of the boot when said well is collapsed due to pressure applied by said thermally expansible material, and

a power piston operably disposed within said well.

10. A thermal power unit in accordance with claim 9 wherein said strain orientating walls form a substantially triangular cross-sectional profile and wherein a longitudinal convex protuberance is formed at the junctions of adjacent strain orientating walls when said well is collapsed due to pressure applied to said boot by said thermally expansible substance.

11. A thermal power unit in accordance with claim 10 wherein said strain orientating walls converge at a common vertex at the base of said well, whereby said Well collapses into a predetermined configuration for resisting misalignment of the boot after extension of the power piston.

12. A thermal power unit comprising:

a casing,

a resilient boot having an opened end and a base portion,

said resilient boot being secured within said casing in such a manner as to form a sealed cavity between said base portion and the inner surface of the casing,

a thermally expansible material disposed in said cavity to compress said boot upon a rise in temperature ambient said casing,

said boot having a well formed therein, said well extending from said opened end into said base portion,

said well having a substantially triangular cylindrical inner surface within said base portion, and

a power piston operably disposed within said well.

13. A thermal power unit in accordance with claim 12 wherein said base portion of said boot has a substantially circular cross-sectional outer profile.

14. A thermal power unit in accordance with claim 13 wherein said power piston comprises a substantially circular cylinder.

15. A thermal power unit in accordance with claim 12 wherein said power piston comprises a substantially circular cylinder having a conical actuation end disposed within said base portion of said boot and wherein the triangular cylindrical inner surface of said well converges to a common apex at the end of the well for receiving the conical actuation end of the piston.

16. In a squeeze type thermal power unit having a casing and a thermally expansible material disposed within the casing, a resilient boot for receiving a power piston and for being disposed in operable contact with the thermally expansible substance, said boot having an opened end, a base portion, and a well extending from the opened end into said base portion, said well having a substantial polygonal cross section, with each angle of the polygon being substantially equal with each other angle thereof and each wall forming the sides of the polygon being of substantially equal length, said boot folding substantially equally along each of the angles of the polygonal cross section in response to pressure applied to the outside of the boot by said thermally expansible substance.

17. In a squeeze type thermal power unit, the combination of a resilient squeeze boot having a 'well for receiving a power member, said well having a substantial polygonal cross section, and a cylindrical power piston having a diameter greater than the diameter of the largest circle contained by said polygonal cross section.

18. A thermal power unit in accordance with claim 17 wherein the plane sides forming said polygonal cross section converge at a common vertex at the base of the well.

19. A power unit comprising:

a casing containing an expansion material,

a sealing member mounted on and closing said casing and having an elongated resilient boot depending therefrom,

a piston well formed along the longitudinal axis of said boot,

said well having at least three flat surfaces along at least a portion of its length adjacent the base of the well, and

a cylindn'cally configunated piston extending from said casing and fitted snugly within said well and having a conically configurated inner end fitted within the base of said well.

References Cited UNITED STATES PATENTS 3,064,477 11/1962 Uernet 73368.3

S. CLEMENT SWISHER, Acting Primary Examiner. WILLIAM HENRY H, Assistant Examiner.

US. Cl. X.-R. 9284, 101 

1. A THERMAL POWER UNIT COMPRISING: A CASING CONTAINING A THERMALLY EXPANSIBLE MATERIAL, A REILIENT BOOT FITTED WITHIN THE CASING IN OPERABLE CONTACT WITH THE THERMALLY EXPANSIBLE MATERIAL, A WELL FORMED WITHIN THE BOOT FOR RECEIVING A RELATIVELY EXTENSIBLE POWER POSITION THEREIN. SAID WELL HAVING AN INNER CROSS-SECTIONAL PROFILE SUBSTANTIALLY TRIANGULAR IN CONFIGURATION, AND 